Radio resource assignment in control channel in wireless communication systems

ABSTRACT

A method in a wireless communication device including receiving ( 410 ) a composite control channel including at least two control channel elements, each control channel element only contains radio resource assignment information, for example, a codeword, exclusively addressed to a single wireless communication entity. The device combines ( 420 ) at least two of the control channel elements, and decodes ( 430 ) the combined control channel elements.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. application Ser. No.14/960,078 filed on Dec. 4, 2015, which is a continuation of U.S.application Ser. No. 11/538,758 filed on 4 Oct. 2006 (now abandoned),the contents of which are incorporated by reference herein and fromwhich benefits are claimed under 35 USC 120.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to wireless communications, andmore particularly to controlling channel signaling for shared channelsin wireless communication systems, for example cellular communicationnetworks, corresponding entities and methods.

BACKGROUND

Time division multiplexing (TDM) and frequency division multiplexing(FDM) methods, including hybrids thereof, have been proposed in additionto separate and joint coding of control channel signaling for schedulingdownlink data transmission in the Long Term Evolution (LTE) of UMTSTerrestrial Radio Access (UTRA) and UTRA Network (UTRAN) specifications.In TDM and FDM transmissions of control channel signaling, the controlinformation for downlink and uplink assignments may be transmitted overthe first few symbols of the downlink frame or it may be spread out overthe length of the frame. The frame duration is approximately 0.5 ms,though other durations are also possible.

The various aspects, features and advantages of the disclosure willbecome more fully apparent to those having ordinary skill in the artupon careful consideration of the following Detailed Description and theaccompanying drawings described below. The drawings may have beensimplified for clarity and are not necessarily drawn to scale.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a wireless communication system.

FIG. 2 illustrates a radio frame comprising a composite control channelhaving a plurality of control channel elements.

FIG. 3 illustrates a composite control channel having different ofcontrol channel element types.

FIG. 4 illustrates a process flow diagram.

FIG. 5 illustrates another process flow diagram.

DETAILED DESCRIPTION

FIG. 1 illustrates a wireless communication system 100 comprisingmultiple cell serving base units forming a network distributed over ageographical region. A base unit may also be referred to as an accesspoint, access terminal, Node-B, or similar terminologies known in theart. The one or more base units 101 and 102 serve a number of remoteunits 103 and 110 within a serving area or cell or within a sectorthereof. The remote units may also be referred to as subscriber units,mobile units, users, terminals, subscriber stations, user equipment(UE), user terminals or by other terminology known in the art. Thenetwork base units communicate with remote units to perform functionssuch as scheduling the terminals to receive or transmit data usingavailable radio resources. The wireless network also comprisesmanagement functionality including data routing, admission control,subscriber billing, terminal authentication etc., which may becontrolled by other network entities, as is known generally by thosehaving ordinary skill in the art.

Base units 101 and 102 transmit downlink communication signals 104 and105 to serving remote units on at least a portion of the same resources(time and/or frequency). Remote units 103 and 110 communicate with oneor more base units 101 and 102 via uplink communication signals 106 and113. The one or more base units may comprise one or more transmittersand one or more receivers that serve the remote units. The number oftransmitters at the base unit may be related, for example, to the numberof transmit antennas 109 at the base unit. When multiple antennas areused to serve each sector to provide various advanced communicationmodes, for example, adaptive beam-forming, transmit diversity, transmitSDMA, and multiple stream transmission, etc., multiple base units can bedeployed. These base units within a sector may be highly integrated andmay share various hardware and software components. For example, allbase units co-located together to serve a cell can constitute what istraditionally known as a base station. The remote units may alsocomprise one or more transmitters and one or more receivers. The numberof transmitters may be related, for example, to the number of transmitantennas at the remote unit.

In one embodiment, the communication system utilizes OFDMA or a nextgeneration single-carrier based FDMA architecture for uplinktransmissions, such as interleaved FDMA (IFDMA), Localized FDMA (LFDMA),DFT-spread OFDM (DFT-SOFDM) with IFDMA or LFDMA. In other embodiments,the architecture may also include the use of spreading techniques suchas direct-sequence CDMA (DS-CDMA), multi-carrier CDMA (MC-CDMA),multi-carrier direct sequence CDMA (MC-DS-CDMA), Orthogonal Frequencyand Code Division Multiplexing (OFCDM) with one or two dimensionalspreading, or simpler time and frequency division multiplexing/multipleaccess techniques.

Generally, a wireless communication network infrastructure schedulingentity located, for example, at each base unit 101 and 102 in FIG. 1,allocates or assigns radio resources to remote units in the network. Thebase units each include a scheduler for scheduling and allocatingresources to remote units in corresponding serving areas or cells orsectors. In multiple access schemes such as those based on OFDM methodsand the long term evolution of UTRA/UTRAN Study Item in 3GPP (also knownas evolved UTRA/UTRAN (EUTRA/EUTRAN)), scheduling may be performed inthe time and frequency dimensions using a Frequency Selective (FS)scheduler. In some embodiments, each remote unit may provide a frequencyband channel quality indicator (CQI) or other metric to the scheduler toenable scheduling.

In OFDM systems or OFDM like systems such as DFT-SOFDM and IFDMA, aresource allocation is a frequency and time allocation that mapsinformation for a particular base unit to sub-carrier resources from aset of available sub-carriers as determined by the scheduler. Thisallocation may depend, for example, on the frequency-selectivechannel-quality indication (CQI) or some other metric reported by the UEto the scheduler. The channel-coding rate and the modulation scheme,which may be different for different portions of the sub-carrierresources, are also determined by the scheduler and may also depend onthe reported CQI or other metric. In code division multiplexed networks,the resource allocation is code allocation that maps information for aparticular base unit to sub-carrier resources from a set of availablesub-carriers as determined by the scheduler.

FIG. 2 illustrates a frame 200 that constitutes a portion of a radioframe. The radio frame generally comprises a plurality of frames, whichmay form a concatenated continuum of frames. In FIG. 2, each frameincludes a composite control channel portion 210 comprising at least twocontrol channel elements. FIG. 2 illustrates the composite controlchannel include a plurality of control channel elements 212, 214, 216and 218. The control channel elements each comprise a codeword thatprovides a physical mapping of a logical control channel to a sequenceof symbols, for example, QAM symbols. The control channel elements aregenerally not the same type. In FIG. 2, for example, control channelelements 212 and 218 have different sizes. Control channel elements mayalso be for uplink or downlink assignments, and have differentassociated information payload. Control channel elements may also beassociated with different releases of the specification. In someembodiments, the composite control channel includes reference symbols,for example, pilot symbols, that are distinct from the control channelelements. The reference symbols are typically read by all remote units.

Each frame corresponds to a transmission time interval (TTI). Anexemplary TTI is 1 ms. In one embodiment, a single TTI has a length 1 msor 2 ms wherein the TTI is segmented into two sub-frames each having a0.5 ms length. Such a construction however implies the need to addressmultiple resource blocks, i.e., more than the number of resource blocksin a single 0.5 ms sub-frame, unless the resource block (RB) definitionis expanded to automatically define the RB as extending over the entirelength of the TTI, without regard for the TTI duration. This can lead toinefficiency, however, in the form of excessive per-RB capacity. In casethe RB is defined to extend over a fraction of the length of the TTI, itwould be possible to independently address each of the resource blocksin the multiple sub-frames making up the TTI. Accordingly mechanisms arerequired to signal resource assignments in the case of a frame or TTIcomposed of concatenated sub-frames. Furthermore, mechanisms arerequired to be able to assign resources based on the needs of individualUE wherein fewer resources being assigned for a UE served smallerpackets while more resources assigned to UE served with larger packets.In the case of UMTS (Universal Mobile Telecommunications System), a TTIis defined as the length of time over which a transmission or transportblock is transmitted. A transmission block or transport block iscomposed of a block of jointly coded data protected by a single CRC. Inthe present instance, an alternate definition of TTI could be the lengthof transmission controlled by a single instance of control channelsignaling.

In one embodiment, each control channel element contains only radioresource assignment information, for example, a codeword, exclusivelyaddressed to a single wireless communication entity, for example, one ofthe remote units 102, 103 in FIG. 1. The radio resource assignmentinformation includes, among other remote unit specific information and atime-frequency radio resource assignment. In other embodiments, theradio resource assignment information may additionally comprisemodulation, code rate, information block size, antenna mode indicator,and other information.

In one embodiment, the wireless communication network infrastructureentity, for example, the scheduler, may address more than one controlchannel element to the same wireless communication entity, for example,one of the remote units 101 or 103 in FIG. 1. More particularly, thecontrol channel may include a first version of a codeword including aresource assignment on a first control channel element of the compositecontrol channel and a second version of the codeword including aresource assignment on a second control channel element of the compositecontrol channel, wherein both of the first and second versions of thecodeword are addressed to the same mobile unit. In one embodiment, thefirst and second versions of the codeword are the same, and in anotherembodiment the first and second versions of the codeword are different.Whether codes words addressed to the same entity are different or thesame affects how the addressed entity combines the control channelelements as discussed further below. Thus the wireless communicationnetwork infrastructure entity transmits the composite control channelincluding at least two control channel elements, wherein each elementsincludes corresponding first and second codeword versions addressed tothe same entity. In some instances, the wireless network infrastructureentity may, typically based on the channel conditions of the entity,transmit the composite control channel including a single controlchannel element addressed to the entity.

In embodiments where the composite control channel includes a compositecontrol channel including at least two different types of radio resourceassignment control channel elements, the remote unit generallydetermines the number of types of control channel elements constitutingthe composite control channel upon receiving the composite controlchannel. In one embodiment, the composite control channel includes typeindicator information for each type of control channel elementconstituting the composite control channel. The remote unit may thusdetermine the number of types of control channel elements based on thetype indicator information. In FIG. 3, a radio frame 300 includes acomposite control channel 310 comprising a first control channel elementtype 312 and a second control channel element types 316. The firstcontrol channel element type is identified by a first indicator, forexample, a sequence of bits, 314 appended to a last control channelelement of the first type. The second control channel element type isidentified by a second indicator 318 appended to a last control channelelement of the second type. In another embodiment, the indicators 316and 318 are not present, and the control channel element type isdetermined after successful decoding of the control element. Forexample, a type bit may indicate an uplink or downlink control elementin the decoded payload. The control element may be addressed to a singleUE by a color coded CRC or by other means. According to another aspectof the disclosure, the remote unit determines a number of controlchannel elements constituting at least one or at least two controlchannel elements of the composite control channel. FIG. 3 is only oneillustrative embodiment of the physical layout of the control channelelements on the radio-sub frame. In an alternate embodiment, the layoutmay be viewed as a logical layout, where the control channel elementscomprise a number of sub-carriers distributed across the frame.

In one embodiment, the determining the number of types of controlchannel elements constituting the composite control channel includesdetermining a number of uplink control channel elements and determininga number of downlink control channel elements. The number of uplinkcontrol channel elements may be determined based on a first sequence ofbits and the number of downlink control channel elements based on asecond sequence of bits embedded within the frame. In one embodiment,the numbers of uplink and down link control channel elements aredetermined based on where the first and second bit sequences areembedded within the frame. Alternatively, the use of different bitsequences may be used to indicate the different numbers of controlchannel elements. For example, a first bit sequence may indicate a firstnumber of uplink elements and a second bit sequence may indicate asecond number of uplink elements.

In some embodiments, the composite control channel includes a firstcomposite control channel portion in a first receive bandwidth on firstcenter frequency and a second composite control channel in a secondreceive bandwidth on a second center frequency. Such a control channelstructure may be implemented to accommodate remote users having limitedreceive bandwidth. More generally, the composite control channel may bedivided into multiple composite control channel portions oncorresponding center frequencies. For example, terminals may have theirreceiver bandwidths limited to 10 MHz, while the carrier bandwidth is 20MHz. In order accommodate such terminals of limited minimum bandwidthcapability, it might be necessary to map the composite control channelto both the lower 10 Mhz and the upper 10 MHz sub-bands of the 20 MHzcarrier. Terminals with 10 MHz capability camp on either one of theupper or lower sib-bands and receive the respective composite controlchannel.

In the process 400 of FIG. 4, at 410 a wireless communication entity,for example, the remote unit, the terminals receives a composite controlchannel including at least two control channel elements. In oneembodiment, each the control channel element only contains radioresource assignment information exclusively addressed to a singlewireless communication entity.

In FIG. 4, at 420, two or more control channel elements are combinedbefore decoding at 430. Generally, however, the remote unit may attemptto decode a single control channel element without first combiningelements or it may attempt to decode a single control channel elementafter decoding or attempting to decode combined elements. Whether or notany combining is necessary depends generally on whether the remote unitis successful decoding single control channel elements. Combining may berequired, for example, in instances where a cyclic redundancy check(CRC) or other information verification check fails after decoding asingle control channel element, or where decoding is not successful.Information verification typically involves remote unit specificinformation, which may be included in the decoded control channelelement, or masked with the encoded control channel element, or maskedor fed into a CRC for CRC color coding.

In some implementations, each of the plurality of control channelelements has an associated root index, which may be used as a basis forcombining the control channel elements. For example, if the compositecontrol channel comprises 12 control channel elements, 4 of thoseelements may have the same associated root index and may be used as thebasis for decoding and combining and decoding the control channelelements. In embodiments where the control channel is divided intoportions on corresponding center frequencies, as discussed above, theremote unit only combines control channel elements from the same controlchannel portion. In other words, control channel elements from differentcontrol channel portions are not combined.

In some embodiments, the remote unit combines at least two controlchannel elements of the composite control channel, wherein each controlchannel element is of the type that contains only radio resourceassignment information exclusively addressed to a single wirelesscommunication entity. Combining may be required, for example, ininstances where a cyclic redundancy check (CRC) or other informationverification check fails after decoding a single control channelelement, or instances where decoding is not successful. Generally,however, the remote unit may attempt to decode a control channel elementwithout first combining.

In one embodiment, at least two of the control channel elements arecombined by summing soft information derived from first and secondcodeword information, wherein the first codeword information is within afirst control channel element and the second codeword information iswithin a second control channel element. In such a combination, thecombine control channel elements are temporally aligned and superimposed(known as Chase combining). The superposition may involve max-ratiocombining, or adding together log-likelihood-ratios (LLRs), or the like.The assumption here is that the first and second codeword information isaddressed to the same remote unit. If not, either the decoding or theinformation verification check after decoding will be unsuccessful. Inthe case of failure, the remote unit may form a different combination ofcontrol channel elements, for example, by combining a different set ofcontrol channel elements or by combining an additional element.

In another embodiment, at least two of the control channel elements arecombined by rearranging and summing soft information derived fromdifferent first and second codeword information, wherein the firstcodeword information is within a first control channel element and thesecond codeword information is within a second control channel element.For example, the first codeword and second codeword may comprise subsetsof an information set and parity bits generated from a lower ratechannel encoder. The subsets may be non-overlapping or partiallyoverlapping. Soft information corresponding to overlapping codeword bitpositions is typically summed in the remote unit, while non-overlappingbit positions are typically rearranged to an appropriate position fordecoding.

In one embodiment, the remote unite combines the at least two controlchannel elements according to predefined combinations of control channelelements. For example, at least one of the pre-defined combinationsincludes a combination of at least two logically contiguous controlchannel elements. The logically contiguous control channel elements mayor may not be physically contiguous. For example, if a set ofsub-carriers distributed across frequency (a comb) is used for onecontrol channel element, another control channel element may or may notphysically occupy the sub-carriers adjacent to the first control channelelement. Or, if the logical and physical orderings of sub-carriers areidentical, that is, there is a one-to-one mapping of logical andphysical sub-carriers, then logical adjacency implies physical adjacencyand vice versa. In other embodiments, at least two non-adjacent controlchannel elements are combined, wherein the non-adjacent control elementsmay be physical or logical.

In some implementations, the order in which the remote unit attempts tocombine the control channel elements according to the pre-definedcombinations is based on one or more hypotheses or assumptions. Forexample, the control channel elements may be combined based on adetermination of the number of control channel elements constituting thecomposite control channel. Such a determination also includesdetermining the number of control channel elements constituting aparticular type of control channel element in embodiments where thecomposite control channel includes more than one elements type asdiscussed above. The number of control channel elements may bedetermined, for example, based on the existence of control channelelement number information included in the composite control channel.For example, the number of control channel elements may be determinedbased on a sequence of bits appended to the composite control channel.In one implementation, different bit sequences are indicative ofdifferent numbers of control channel elements. In anotherimplementation, the location of the sequence of bits within the frame isindicative of the number of the control channel elements. In this latterimplementation, the same bit sequence may be used to indicate differentnumbers of control channel elements depending on where the bit sequenceis located within the frame. The number of control channel elements mayalso be determined based on data or messaging shared between a wirelesscommunication device and a network infrastructure entity. This may occurin a message sent to all remote units via a broadcast channel sentoccasionally or a broadcast message sent in each TTI. The number ofcontrol channel elements or subset of control channel elements that theremote unit should decode may also be sent via a message dedicated forthat remote unit.

In one embodiment, control channels may be one or two control channelelements, with the size of the control element indicating the type ofcontrol element. Convolutional encoding may be used for the controlelements. And the decoder may decode the first control element, checkthe CRC, and then stop decoding if the control element is designated forthe user. If not, the decoding may commence from the point just prior totail bit insertion on the first control element, through the end of thetrellis comprised of both control elements. The CRC is again checked. Inthis way, control channel decoding may be achieved with less effort thanif combined control elements were decoded from the beginning of thetrellis. Note that the code rate for the single and two control elementsmust be the same in this embodiment.

In some embodiments, a portion of the composite control channel isallocated for assigning radio resources in each frame. In theseembodiments, the unallocated portion of the control channel may be usedfor data transfer. Thus a wireless communication network infrastructureentity, for example, a scheduler, may allocate a portion of the controlchannel for assigning radio resources in each frame by embedding a bitsequence within the corresponding frame. In one embodiment, the locationof the sequence of bits within the frame is indicative of the size ofthe control channel, for example, how many control channel elements areallocated for assigning radio resources to one or more remote units. Inthis implementation, the control channel elements may be addressedexclusively to a single remote unit or to more than one remote unit.More generally, the network infrastructure entity may dynamically changethe portion of the control channel for assigning radio resources in eachframe by changing the bit sequence or the location bit sequence embeddedin each frame before transmitting the frames. As suggested above,moreover, the network infrastructure entity may also dynamicallyallocated different types of control channel elements and the numberthereof within a frame.

In another embodiment, the bit sequence embedded within the sub-frame isused to identify that the control channel element is for a remote unit.In this case, the bit sequence embedded within the sub-frame may be adata dependent bit sequence, such as a CRC processed with wirelesscommunication device identification information, the codeword maskedwith wireless communication device identification information or thelike. In this embodiment, a first sub-frame, which may be the lastsub-frame of a TTI, contains control information including modulationtype, resources, or antenna mode indicator. Each control channel may beone or more control channel elements, and the size of the controlchannel may be different in the first and second sub-frames. The secondsub-frame may occur on the same or different portions of the controlchannel as the control information from the first sub-frame. If adifferent portion of the sub-frame is used, blind decoding complexitymay be reduced by having the control channel elements in the secondsub-frame known from the location of the remote units control channelelements from the first sub-frame.

In the process diagram 500 of FIG. 5, at 510, the wireless communicationnetwork infrastructure entity allocates a portion of the control channelfor assigning radio resources in each frame by embedding a bit sequencewithin the corresponding frame. Allocating a portion of the controlchannel includes allocating all available portions of the controlchannel or less than all available portions thereof, wherein theunallocated portion may be used for other purposes, for example, datatransfer. At 520, the wireless communication network infrastructureentity dynamically changes the portion of the control channel forassigning radio resources in each frame, wherein multiple framesconstitutes a radio frame. According to this aspect of the disclosure,potentially, a different portion of each control channel in each frame,constituting the radio frame, may be allocated to assigning radioresources. The portion of the control channel for assigning radioresources in each frame may be changed dynamically by changing thelocation of the bit sequence embedded in each frame or by usingdifferent bit sequences, as discussed above. At 530, the wirelesscommunication network infrastructure entity transmits at least twoframes, for example, constitute a radio frame, wherein each frameincludes a control channel having a portion thereof allocated for radioresource assignment.

In FIG. 2, for example, a portion of the control channel used for radioresource assignment is indicated based on where a bit sequence 220,referred to as a terminating marker or signature, is embedded within thecorresponding frame. Depending on where the bit sequence is located, theportion of the control channel, e.g., the number of elements, used forradio resource assignment may be less than the entire control channel ofthe frame. Generally, different frames constituting a radio frame mayallocate different portions of the corresponding control channels forradio resource assignment. In one implementation, a wirelesscommunication device, comprises a receiver capable of receiving a framecorresponding to a transmission time interval, wherein the frameincludes a control channel and a bit sequence embedded within the frame.A controller communicably coupled to the receiver is configured fordetermining a portion of the control channel used for radio resourceassignment based on where the corresponding bit sequence is embeddedwithin the received frame, wherein the portion of the control channelused for radio resource assignment may be less than the entire controlchannel.

In the wireless communication device, for example, one of the remoteunits 101 or 103 in FIG. 1, the device receives a plurality of at leasttwo frames, wherein each frame includes a control channel having atleast two control channel elements and each frame includes a bitsequence embedded within the frame. In one embodiment, the wirelesscommunication device determines a portion of the control channel usedfor radio resource assignment in each frame based on where thecorresponding bit sequence is embedded within the frame. Generally, theportion of the control channel used for radio resource assignment may beless than the entire control channel and each frame may use differentportions of the control channel for radio resource assignment based uponwhere the corresponding bit sequences is embedded within the frame.

In some instances, all control channel elements of the composite controlchannel communicate control channel information. In this particularembodiment, the absence of control channel element number information,e.g., a bit sequence embedded within the frame, is indicative of the useof the full composite control channel for radio resource assignment. Forexample, in the absence of control channel element number information,the remote unit may assume a default number of control channel elementsare used for assigning radio resources.

While the present disclosure and the best modes thereof have beendescribed in a manner establishing possession and enabling those ofordinary skill to make and use the same, it will be understood andappreciated that there are equivalents to the exemplary embodimentsdisclosed herein and that modifications and variations may be madethereto without departing from the scope and spirit of the inventions,which are to be limited not by the exemplary embodiments but by theappended claims.

What is claimed is:
 1. A method in a wireless communication device, themethod comprising: receiving a composite control channel including atleast two radio resource assignment control channel elements;determining a number of types of control channel elements constitutingthe composite control channel.
 2. The method of claim 1, the compositecontrol channel including type indicator information for each type ofcontrol channel element constituting the composite control channel,determining the number of types of control channel elements based on thetype indicator information.
 3. The method of claim 2, the type indicatorinformation includes a sequence of bits appended to a last controlchannel element of each type.
 4. The method of claim 1, determining anumber of control channel elements constituting at least one type ofcontrol channel elements of the composite control channel.
 5. The methodof claim 1, determining a number of control channel elementsconstituting at least two types of control channel elements of thecomposite control channel.
 6. The method of claim 1, determining anumber of control channel elements constituting at least one type ofcontrol channel element of the composite control channel.
 7. The methodof claim 1, determining the number of types of control channel elementsconstituting the composite control channel includes determining a numberof uplink control channel elements and determining a number of downlinkcontrol channel elements.
 8. The method of claim 1, determining thenumber of types of control channel elements constituting the compositecontrol channel includes determining a number of uplink control channelelements based on a first sequence of bits and determining a number ofdownlink control channel elements based on a second sequence of bits. 9.The method of claim 8, determining the number of uplink control channelelements based on where the first sequence of bits is embedded withinthe frame and determining the number of downlink control channelelements based on where the second sequence of bits is embedded withinthe frame.
 10. The method of claim 1, wherein the number of types ofcontrol channel elements is determined after successful decoding of thecontrol channel elements, through a type bit included in the decodedpayload.